This invention relates to a coating composition to protect and lubricate, if desired, the surface of an article without adversely affecting or otherwise degrading the physical properties of the article onto which the coating is applied. More particularly, the present invention relates to using such a coating to form a lubricant and/or wetting agent for the surface of a cable to be pulled through a conduit, duct or raceway and to form a lubricant for the passage of mixed concrete through a conduit or duct.
The coating of the present invention is used to form a lubricant to facilitate movement of a cable or a mass of mixed concrete through a die, conduit or duct. During the pulling of cable, the ever-present problem of friction occurs between the outside surface of the cable being pulled and the inside surface of the passageway. From an economic standpoint, it is desirable to use the longest possible length of cable during a single pull through the conduit or duct. However, as the length of cable involved in a single pull increases, there is a corresponding increase to the necessary pulling force imposed on the cable. If an excessive pulling force is developed, the cable elongates beyond an allowable value causing fractures or breaks to occur. After a cable is drawn into a conduit or raceway, it is frequently necessary to move the cable in a reverse direction to facilitate dressing operations to the surface of the cable sheathing. Back and Forth adjustments to the position of cable within a conduit is required when the preselected lengths of cable have their ends pre-equipped with a system of connectors.
In the past, a thixotropic paraffin-based gel, or petroleum-based lubricant was applied by hand onto the surface of the cable preparatory to the pulling operation. An applicator system such as is disclosed in U.S. Pat. No. 4,028,473, eliminated much of the labor and mess usually associated with manual application of the lubricant onto the cable. However, a heavy residue of lubricant remains on the surface of the cable whereby the necessary splicing operations were impeded because of the residue particularly in an underground environment.
Instead of a thixotropic paraffin-based gel or petroleum-based lubricant, there is disclosed in U.S. Pat. No. 3,925,216, a lubricant comprised of polyethylene oxide in an alcohol-water solution. Such a lubricant will eliminate much of the clean-up operations because it provides a desirable property of rapid evaporation. However, this lubricant has inferior friction-reducing properties as compared to a thixotropic gel, particularly in regard to the necessary cable dressing operations and back and forth adjustments of the cable when using selected lengths with pre-prepared connectors. A lubricant of polyethylene oxide in an alcohol-water solution will rapidly evaporate and is highly water-soluble whereby little lubricant, if any, remains after the pulling operation is completed. However, this lubricant composition can be useless or ineffective when the ductwork contains or is filled with water as frequently occurs when the ductwork is underground.
Detrimental effects due to friction occur at the inside surface of a passageway as a mass of mixed concrete is forced to move along the passageway. The present-day practice of transporting mixed concrete by a pump from a vehicle to the actual job site offers many advantages. The mixed concrete is moved in a conduit which is made of steel, aluminum or plastic materials to provide strength and abrasion resistance. The conduit usually includes articulated joints or the like so that the conduit can be placed to extend along the desired course. Because of the pressures involved, the power needed to move mixed concrete over a given height or distance is necessarily large, particularly because of the weight of the concrete (e.g., 4000 lbs per cubic yard). However, by using an effective lubricant along the inside wall of the conduit, the concrete mixture will pass more effeciently along the conduit and through articulated joints. The lubricant not only minimizes the loss of power due to friction but also minimizes a liquid-to-solid phase segregation to the concrete due to its movement along the conduit. In this regard, a homogenous concrete mixture is known to undergo segregation into aggregate phase and a cement-paste phase which sometimes undergoes further separation into a water and thick cement-paste phase.